ausblenden:
Schlagwörter:
pollen; Lake Baikal; last glacial–interglacial transition; Younger Dryas; Holocene; Progress towards reconstructing past climate in Central Eurasia, with special emphasis on Lake Baikal
DDC:
550 - Earth sciences
Zusammenfassung:
High-resolution pollen records from Lake Baikal revealed considerable regional differences in the vegetation development and pronounced climate variability during the last glacial–interglacial transition and Holocene. Correlation between cores was successfully based on a chronology constructed from AMS 14C dating of pollen concentrates. Comparison to other radiocarbon-dated pollen sequences from the Baikal region suggests that the chronology presented is very reliable, and thus correlation to other dated events can easily be performed. Pollen indices, which reflect relative changes in major vegetation types and limitations of growing conditions by moisture availability and temperature, demonstrate near-synchronous vegetation changes, which suggest synchronous large-scale climate variation across the Baikal region. Due to the limited influence of human impact in the Lake Baikal region, the pollen data illustrate that, in the continental interior of NE Eurasia Holocene, climate variability was very pronounced. After initial warming and a strong increase in relative moisture (ca. 16 cal ka BP), the Bølling–Allerød-like event was punctuated by three cool and dry events. These events, dated between ca. 15 and 13 cal ka BP, can be compared to coolings as recorded in GISP 2 oxygen isotope records from Greenland ice cores. An expansion of Betula sect. Nanae/Fruticosae, Artemisia and Chenopodiaceae marks the Younger-Dryas (YD)-like cooling event (ca. 12.5–12 cal ka BP). High temperatures and favourable moisture conditions during the first part of Holocene favoured the optimum development of dark coniferous taiga between 11–7.5 cal ka BP in the south and 10–8 cal ka BP in the northeast. A fir and spruce decline in the southern mountains (ca. 9.5–8.5 cal ka BP) can be related to the 8.2 cal ka BP cooling event. The pronounced mid-Holocene cooling event and a transition towards dry conditions (ca. 8–7 cal ka BP) preceded the nearly synchronous regional expansion of pine taiga. Maximum distribution of Scots pine forests marks the Holocene thermal optimum (ca. 6.5–5.7 cal ka BP), which was followed by two subsequent cooling events (ca. 5.5–4.5 cal ka BP) at the Atlantic–Subboreal transition. A subsequent temperature optimum in the southeastern Baikal region ended with pronounced cooling during the Subboreal–Subatlantic transition (ca. 3–2.5 cal ka BP). A late spread of shrub alders may evidence the beginning of the Little Ice Age.
